A Eurasian native, rather aggressively spreading underground to form persistent weedy colonies along roadsides and railroads, in yards and thickets, and in disturbed places such as dumping areas. First collected in 1893 in Jackson Co.

The blue flowers are in a ± one-sided raceme and the reflexed calyx lobes are distinctive; the capsules open by pores near the base, as in C. trachelium, but unlike C. persicifolia.